I'm working on creating an FM radio using the Si4705 chip. I decided to design and build my own breakout board since Sparkfun's does not have the digital audio pins connected to the header.
I noticed on their schematic that they put 330ohm resistors inline with SDIO and SCLK. But from my research, it looks like most I2C system just connect to the microcontroller directly, without inline resistors. Am I missing something here?
Ultrasafe circuit design; the user may inadvertently miswire such a signal to gnd or vcc; without the resistor, survival of pin driver is chancy, whereas with that resistor no foul occurs.
If no reason exists to leave it out, all my designs get that treatment, though with the relatively rugged Nano I use 220 ohm.
Interesting. I had a feeling it would be something like that.
I’m having trouble communicating with my Si4705 and was wondering if this may have had something to do with it.
The U1 inputs have input diodes to 3v3.
If you were to put a 5v signal on these pins, the diodes would get wiped out . . .
The resistors prevent this kind of damage.
Less reliable design. The serial resistors become part of a voltage divider that decreases the signal/noise ratio.
Ahh yes. The theoretical maximum vs practical design practices. You win, of course, in theory.
See I was kind of thinking the same thing. I was thinking maybe it's "more robust" but at the same time "less reliable" because of the voltage divider.
I suspect Sparkfun did this because they're catering to hobbyist and perhaps even young students that might make "less than ideal" connections. lol
Shall I just try replacing these with 0 ohm resistors (or just solder) for now? I think I will.
Sure, if this isn't your first rodeo, go for it. You understand the risk.
You were right!
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